A
mineral or hard material that can be
cut,
polished, and used in
jewelry. Also called
gem.
Gemstones are evaluated using four major criteria: beauty, rarity, durability, and desirability. A valuable gemstone must be pretty, not too common, hold up under wear, and be of good quality. (See what attributes make a gemstone desirable?.)
Gemstones are sometimes divided into the categories of precious stones (diamond, emerald, ruby and sapphire; sometimes also pearl) and semiprecious stones (anything that isn't precious but is capable of jewelry use). Nonprecious stones wouldn't be considered gemstones.
Related concepts:
Durability: Mohs hardness scale, tenacity, cleavage
Weight: Carat (not karat), point, grain
Cut: Facet, Cabochon, Lapidary
Gem phenomena: Adularescence, Asterism, Aventurescence, Chatoyancy, Color change, Color play, Color zoning, Fluorescence, Iridescence, Pleochroism.
Other: Gem enhancement, Synthetic gems, Simulant (Cubic zirconia)
Specific gemstones:
Calcite
Chalcedony
Chrysoberyl
Coral
Corundum
Danburite
Diopside
Dioptase
Diamond
Feldspar
Fluorite
Garnet
Hematite
Iolite
Ivory
Jade
Jet
Kyanite
Lapis Lazuli
Malachite
Milarite
Moldavite
Obsidian
Opal
Pearl
Peridot
Quartz
Rhodochrosite
Rhodonite
Scapolite
Serpentine
Sillimanite
Sodalite
Spinel
Spodumene
Titanite
Topaz
Tortoiseshell
Tourmaline
Turquoise
Zircon
Zoisite